This invention relates in general to devices for drilling holes in the ground and, more specifically, to a system for drilling holes at a considerable distance from the drill support structure.
A wide variety of earth drilling machines have been developed for drilling large and small diameter holes of various depths in different soils under widely varying conditions. While the prior systems have been able to overcome many drilling problems, none have been capable of efficiently drilling holes on unstable hillsides or unstable ground where no nearby stable surface for supporting a drilling rig is available.
Most commercial drilling rigs are designed to support a drilling head on a tower or boom extending vertically directly above the hole site. Typical of these are the arrangements disclosed by Burg et al. in U.S. Pat. No. 2,728,555 and Wilson in U.S. Pat. No. 3,191,450. Such devices are cumbersome, often requiring on-site assembly, and cannot be directly used on unstable ground or hillsides.
Portability of drill rigs has been improced by cantilevered crane- or truck-mounted drill rigs, such as are described by H. R. Smith in U.S. Pat. No. 1,895,901 and E. A. Smith in U.S. Pat. No. 1,971,922. In these cases, the drilling head can be extended in a cantilevered fashion beyond the end of the supporting vehicle. The extension distance is, however, quite limited, because, among other things, a horizontal bar extending from the vehicle to the drilling head must absorb the drilling torque. Also, the extension is primarily horizontal, so that drilling on hillsides above or below the support vehicle is difficult.
On a tower mounted drill, additional drilling pressure may be directly transmitted from the tower to the drill. On the cantilevered drill systems, the drilling pressure is limited to that provided by the drill and drilling head, which is often insufficient for rapid, efficient drilling in some soils.
Thus, there is a continuing need for improved systems for drilling at an increased distance from the support vehicle.